1. Field of the Invention
The present invention relates to an audio signal processor.
2. Description of the Prior Art
It is known to associate audio data samples with video data. This is done, in the SDI standard (Serial Digital Interconnect) defined by SMPTE. The SDI audio standard is defined by SMPTE: see SMPTE 272M: "Formatting AES/EBU Audio and Auxiliary Data into Digital Video Ancillary Data Space"- SMPTE Journal, April 1994. In SDI digital audio data is embedded in digital video data.
NTSC signals have a rate of 59.94 fields per second, 29.97 frames per second. In for example SDI the audio data is sampled at 48 KHz per channel, with the sample clock locked to the television signal. This results is a non-integer number of audio samples per frame: EQU 48000/29.97=1601.6
to one decimal place.
There is however an integer number 8008 of samples per 5 frame sequence. However with the 5 frame sequence there are 1602 samples in 3 frames and 1601 samples in 2 frames. This causes difficulties for storing and editing. It is necessary to identify the individual audio frames in each sequence. Variable size storage is required. If a sequence is edited, in four out of five cases, the sequence will be broken requiring samples to be added or subtracted from the resulting edited sequence to restore the sequence to its correct numbers of samples in each frame of the sequence.